1. Field of the Invention
The present invention relates to a satellite communication system and a routing method using the same and particularly, a satellite communication system for performing communications through an artificial satellite and an earth station and a routing method using the same.
2. Description of the Related Art
Since a satellite communication system can cover a broad area, it is used for not only communications between fixed stations (earth stations), but also mobile communications.
When the satellite communication system is applied to mobile communications, a DAMA (Demand Assigned Multiple Access) system for assigning a line every time a communication request occurs is used to efficiently use the satellite communication system because communication requests sporadically are made from many mobile terminals.
Furthermore, in the satellite communication system, satellites and earth stations have been developed in performance, and compact antennas of about 1 m (meter) in diameter have been usable as the frequencies used in the satellite communication system are shifted from a C band (4/6 GHz band) to Ku band (12/14 GHz band).
Earth stations using such compact antennas are called as VSAT (Very Small Aperture Terminal), and they are dispersively located at many places. It is general that a lot of data are transmitted to each of the earth stations through a key (master) station equipped with a large-scale antenna.
In a VSAT satellite communication system using VSAT, a line from a key station to VSAT is called as an out-bound line, and a line from VSAT to a key station is called as an in-bound line. The out-bound line carries out data communications at a high transmission speed, and it uses a TDM (Time Division Multiple) system to perform data multiplexing for each VSAT. The in-bound line carries out data communications from many VSATs at a low transmission speed, and it uses a packet transmission or the DAMA system described above.
A router is generally used as a routing portion. The VSAT satellite communication system is used for checking/introduction of credit cards and transmission of POS (Point Of Sales) data in retail trades, data transmission between an on-line terminal and a host computer in financial business, and transmission of reservation data for hotels, rental cars or the like.